[swift-evolution] When to use argument labels, part DEUX

[Radosław Pietruszewski]

>>>> but I want to make sure if I interpret the proposed guidelines right.
>>>> 
>>>> 	func actionForCommand(command: UIKeyCommand) -> String? {
>>>> 
>>>> This should become “actionFor(command: c)” — which isn’t an obvious
>>> 
>>> That looks like a call, in which case the API above doesn't allow an
>>> argument label.
>> 
>> I’m sorry — I got confused — what do you mean here?
> 
> Sorry, I didn't notice that you both transitioned from declaring
> (actionForCommand(_)) to calling (actionFor(command:)) *and* changed the
> API at the same time.
> 
> So, I would say the guidelines say the call should look like:
> 
>    b.action(for: c)
>> 
>>> 
>>>> It should be `createAttribute(tag: t, data: d)`. 
>>> 
>>> Again that looks like a call, so for the above declaration it would be
>>> 
>>>     createAttribute(t, d)
>>> 
>>>> Alternatively, it could be `attributeFor(tag: t, data: d)` — I could
>>>> go either way.
>>> 
>>> Why “for?” Can you explain the semantics of this method (or show a BCDC)?
>> 
>> This is a initializer-like helper method that instantiates a
>> SecKeychainAttribute from passed parameters.
> 
> If it's a factory, I think guidelines prescribe the call should look like:
> 
>   makeAttribute(tag: t, data: d)

So that’s interesting, because there’s a difference in convention between a factory/initializer-like function:

	makeFoo(this:, that:)

and a getter/finder-like function:

	foo(withThis:, that:)

I think that (in particular the difference in the treatment of argument labels) is the part that makes me most uncomfortable about the latest draft. Perhaps it isn’t such a big deal, since you usually don’t see the two next to each other, and as was noted, most finder-like functions only come with a single parameter, while initializers and factory methods very commonly have many parameters...

Best,
— Radek
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